Field of the Invention
The present invention relates to abdominal aortic aneurismal devices and more particularly to a guiding device of the delivery system which facilitates cannulation of the contra-lateral leg of a Bifurcated Stent or Bifurcated Stent Graft in-vivo and the method of use.
Discussion of the Related Art
An aneurysm is an abnormal dilation of a layer or layers of an arterial wall, usually caused by a systemic collagen synthetic or structural defect. An abdominal aortic aneurysm is an aneurysm in the abdominal portion of the aorta, usually located in or near one or both of the two iliac arteries or near the renal arteries. The abdominal aortic aneurysm often arises in the infrarenal portion of the diseased aorta, for example, below the kidneys. A thoracic aortic aneurysm is an aneurysm in the thoracic portion of the aorta. When left untreated, the aneurysm may rupture, usually causing rapid fatal hemorrhaging.
Aneurysms may be classified or typed by their position as well as by the number of aneurysms in a cluster. Typically, abdominal aortic aneurysms may be classified into five types. A Type I aneurysm is a single dilation located between the renal arteries and the iliac arteries. Typically, in a Type I aneurysm, the aorta is healthy between the renal arteries and the aneurysm, and between the aneurysm and the iliac arteries.
A Type II A aneurysm is a single dilation located between the renal arteries and the iliac arteries. In a Type II A aneurysm, the aorta is healthy between the renal arteries and the aneurysm, but not healthy between the aneurysm and the iliac arteries. In other words, the dilation extends to the aortic bifurcation. A Type II B aneurysm comprises three dilations. One dilation is located between the renal arteries and the iliac arteries. Like a Type II A aneurysm, the aorta is healthy between the aneurysm and the renal arteries, but not healthy between the aneurysm and the iliac arteries. The other two dilations are located in the iliac arteries between the aortic bifurcation and the bifurcations between the external iliacs and the internal iliacs. The iliac arteries are healthy between the iliac bifurcation and the aneurysms. A Type II C aneurysm also comprises three dilations. However, in a Type II C aneurysm, the dilations in the iliac arteries extend to the iliac bifurcation.
A Type III aneurysm is a single dilation located between the renal arteries and the iliac arteries. In a Type III aneurysm, the aorta is not healthy between the renal arteries and the aneurysm. In other words, the dilation extends to the renal arteries.
A ruptured abdominal aortic aneurysm is presently the thirteenth leading cause of death in the United States. The routine management of abdominal aortic aneurysms has been surgical bypass, with the placement of a graft in the involved or dilated segment. Although resection with a synthetic graft via transperitoneal or retroperitoneal procedure has been the standard treatment, it is associated with significant risk. For example, complications may include peri-operative myocardial ischemia, renal failure, erectile impotence, intestinal ischemia, infection, lower limb ischemia, spinal cord injury with paralysis, aorta-enteric fistula, and death. Surgical treatment of abdominal aortic aneurysms is associated with an overall mortality rate of five percent in asymptomatic patients, sixteen to nineteen percent in symptomatic patients, and is as high as fifty percent in patients with ruptured abdominal aortic aneurysms.
Disadvantages associated with conventional surgery, in addition to the high mortality rate, include an extended recovery period associated with the large surgical incision and the opening of the abdominal cavity, difficulties in suturing the graft to the aorta, the loss of the existing thrombosis to support and reinforce the graft, the unsuitability of the surgery for many patients having abdominal aortic aneurysms, and the problems associated with performing the surgery on an emergency basis after the aneurysm has ruptured. Further, the typical recovery period is from one to two weeks in the hospital and a convalescence period, at home, ranging from two to three months or more, if complications ensue. Since many patients having abdominal aortic aneurysms have other chronic illnesses, such as heart, lung, liver and/or kidney disease, coupled with the fact that many of these patients are older, they are less than ideal candidates for surgery.
The occurrence of aneurysms is not confined to the abdominal region. While abdominal aortic aneurysms are generally the most common, aneurysms in other regions of the aorta or one of its branches are possible. For example, aneurysms may occur in the thoracic aorta. As is the case with abdominal aortic aneurysms, the widely accepted approach to treating an aneurysm in the thoracic aorta is surgical repair, involving replacing the aneurismal segment with a prosthetic device. This surgery, as described above, is a major undertaking, with associated high risks and with significant mortality and morbidity.
Over the past five years, there has been a great deal of research directed at developing less invasive, endovascular, i.e., catheter directed, techniques for the treatment of aneurysms, specifically abdominal aortic aneurysms. This has been facilitated by the development of vascular stents, which can and have been used in conjunction with standard or thin-wall graft material in order to create a stent-graft or endo-graft. The potential advantages of less invasive treatments have included reduced surgical morbidity and mortality along with shorter hospital and intensive care unit stays.
Stent-grafts or endoprostheses are now Food and Drug Administration (FDA) approved and commercially available. Their delivery procedure typically involves advanced angiographic techniques performed through vascular accesses gained via surgical cut down of a remote artery, which may include the common femoral or brachial arteries. Over a guidewire, the appropriate size introducer will be placed. The catheter and guidewire are passed through the aneurysm. Through the introducer, the stent-graft will be advanced to the appropriate position. Typical deployment of the stent-graft device requires withdrawal of an outer sheath while maintaining the position of the stent-graft with an inner-stabilizing device. Most stent-grafts are self-expanding; however, in some cases an additional angioplasty procedure, e.g., balloon angioplasty, may be required to secure the position of the stent-graft. Most stent-grafts for percutaneous treatment of abdominal aortic aneurismal disease frequently have a proximal portion or trunk with a single proximal lumen that then bifurcates into two distal lumens of a smaller diameter than the diameter of said proximal portion. The distal lumens may have equal or unequal lengths. The proximal trunk portion of this bifurcated stent graft, being in fluid communication with each of the two distal lumens allows for uninterrupted fluid flow though the entire stent graft while excluding any flow into the aneurismal space.
Due to the large diameter of the above-described devices, typically greater than twenty French (F) (whereas 3 F=1 mm), arteriotomy closure typically requires suturing to facilitate the healing process. Some procedures may require additional surgical techniques, such as hypogastric artery embolization, vessel ligation, or surgical bypass in order to adequately treat the aneurysm or to maintain blood flow to both lower extremities. Likewise, some procedures will require additional advanced catheter directed techniques, such as angioplasty, stent placement and embolization, in order to successfully exclude the aneurysm and efficiently manage leaks.
As one increases the profile of the device, the difficulty in delivering the device also increases. The market today is populated by devices approximately 20 F and greater requiring the need for a surgical cut-down approach utilizing catheters, guidewires and accessory devices. Although devices of this size may substantially eliminate the need for open surgical intervention and the cut-down approach significantly reduces the acute complications that often accompany open surgical intervention, the ultimate goal and the market trend is to reduce delivery system profiles below 20 F, and thus be able to perform the procedure of delivering an endoprosthesis percutaneously, as by the Seldinger technique, which eliminates the need for the cut-down procedure.
Given the large profile of Abdominal Aortic Aneurysm devices, there is a significant motivation to reduce profile. In order to reduce profile, the stents comprising the bifurcated legs are sometimes staggered relative to one another so that they are nested during delivery. By staggering the stent components of the bifurcated section, although a reduced profile can be achieved, the column strength of each leg may be somewhat compromised, this may in turn lead to a cannulation difficulties into the bifurcated legs. An alternative method in which to accomplish a reduction in overall profile is to assemble the resulting stent graft in the vessel by delivering the portions or sections of the device individually. With individual delivery of the portions, the overall resulting profile may be significantly reduced for each individual portion relative to the overall resulting profile in the situation when the entire device is delivered simultaneously. With a staged delivery as described, cannulation of the previously implanted portion is critical in locating the subsequently delivered portion and to ensure that inter-operative assembly of the individual portions is successful.
In addressing Abdominal Aortic Aneurismal disease, frequently, the initial stent-graft will be supplemented by the use of one or more additional stent-grafts, also known as endo-legs. By delivering the endo-legs separately, one can achieve the previously stated objective of reduced profile. The purpose of these endo-legs allows extension of one or both of the distal lumens of the initial stent-graft into each of the corresponding iliac arteries to allow for a continuous and uninterrupted flow path from the aorta into the respective iliac arteries and to ensure complete exclusion of the aneurysm. To ensure the continuous flow path, proper placement and securing of the endo-leg into the corresponding distal lumen of the initial stent graft is critical. Improper placement of the endo-leg may result in poor fixation and/or anchoring of the device. In addition improper placement may result in a poor fit of the endo-leg in the distal lumen of the initial stent-graft, which may result in endo-leaks as the uninterrupted flow path would be compromised.
While the above-described endoprostheses represents a significant improvement over conventional surgical techniques, there is a need to improve the endoprostheses, particularly their method of use and delivery and their applicability to varied biological conditions. Accordingly, in order to provide a safe and effective means for treating aneurysms, including abdominal aortic aneurysms as well as other cases where bifurcated stents or stent-grafts are utilized, a number of difficulties associated with currently known endoprostheses and their delivery systems must be overcome. One concern with the use of endoprostheses as described above, specifically the efficient and proper placement of an extension leg, is the ease of which access to the lumen of the device, or in the case of an abdominal aortic aneurismal device, the ease of which access to the contra-lateral leg of the initial stent-graft with a guide-wire can be achieved. This ease of use is directly correlated to the time required to achieve this objective, with time in this case being the interventionalist's enemy.
With the placement of abdominal aortic aneurismal devices, the trunk and distal lumen portions of the device are usually delivered with a delivery system that frequently utilizes a first guidewire, commonly referred to as the ipsilateral guidewire. Typically, said trunk and one of the distal lumens of the device tracks over said ipsilateral guidewire, meaning the ipsilateral guidewire is positioned within the interior of the device, through the trunk and one of the distal lumens of the initial graft. Proper placement of the guidewire essentially facilitates proper placement of the trunk portion and one of the distal lumen portions as well as at least one of the endo-legs providing an extension of the distal lumen when the corresponding endo-leg is subsequently delivered over said ipsilateral guidewire.
With the first endo-leg properly positioned, access to the contra-lateral leg of the device is normally performed with a second guidewire, and achieved by feel and experience of the physician directing the guidewire external to the body to control movement within the vessel augmented by the real-time fluoroscopic image provided. This can be an extremely difficult and time consuming task in normal vessels and the difficulty and time may significantly increase in tortuous vessels, highly angulated vessels, partially diseased vessels, calcified vessels, odd shaped vessels, short vessels, and/or long vessels all of which are quite common. The addition of both time and difficulty to the procedure may affect patient outcome. It is also desirable to limit exposure time to the various contrast agents utilized that enable real-time fluoroscopic imaging.
Accordingly, there exists a need for obtaining quick, easy, and efficient access of guidewires into the lumen of a previously placed device. It would be particularly advantageous to facilitate placement of a guidewire into the contra-lateral leg of an abdominal aortic aneurismal device.
In placing abdominal aortic aneurismal devices, it would also be advantageous to utilize in some way the existing delivery system over the first guidewire that placed the initial graft, to facilitate placement of the second guidewire into the contra-lateral leg of the initial graft given the relationship of the locations of the first and second guidewires ordinarily used in such a procedure.